A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Arthur Pearson
Date: 2002 Nov 24, 11:46 -0500
Ladies and Gentlemen:
I am interested in learning more about Lewis and Clark’s navigational procedures. There has been some tangential mention on this list about their lunar methods of obtaining longitude. I am particularly curious about how closely their methods conformed to our recent discussion, “Re: Use of Sun Sights for Local time, and Lunars for Longitude”. Stephen Ambrose’s book “Undaunted Courage” provides glimpses into how they worked, including the following:
· In Philadelphia, 1803, Lewis acquired “A Practical Introduction to Spherics and Nautical Astronomy” and “The Nautical Almanac and Astronomical Ephemeris” as well as “tables for finding latitude and longitude” (p. 91).
· At one location along the Missouri, Lewis “measured the distance between the sun and the moon’s nearest limb forty-eight times…. He faithfully recorded whatever he could whenever he could, leaving up to experts back east to work out the meaning of the figures” (p. 148).
· Ambrose states that “...he wrote a thousand-word description of the instruments he was using, how he was using them, what he was measuring, and so forth. It seems Lewis wanted to be as sure as he could tat someone someday would take all his figures and make some sense of them.”
Has anyone on the list examined that thousand word description of how Lewis made his celestial observations? Would the tables he acquired in Philadelphia have been Bowditch’s recently published “New American Practical Navigator”? Is there an essay or paper anywhere on this topic of his celestial procedures? Any insight or direction to additional sources would be most welcome.